Touch sensitive display panels have been developed to provide a user interface to various types of systems. For example, touch sensitive user interfaces have been provided for computing and data processing systems, as well as for various types of diagnostic and testing equipment. Touch sensitive interfaces enable a user to select among various control keys displayed on a display panel. The user selects a desired control key by touching the display panel in a touch zone that corresponds to the desired control key. The touch zone for each control key on the display panel generally corresponds to the area on the display panel where the control key is displayed. Since it is often desirable to display many control keys on a display panel simultaneously, the display area for each control key is often rather small. As a result, a problem is encountered in many touch sensitive user interface systems. If the user does not touch the display panel within the small display area for the desired control key, the desired control key is not selected.
Another problem is encountered in touch sensitive user interface systems when the control key display area is small in relation to the size of a probe that the user must touch to the display panel in order to select a desired control key. In many touch sensitive user interface systems, the user's finger serves as the probe and the size of the average finger tip is often large in relation to the display area utilized to display the control keys. Therefore, touch sensitive user interface systems that limit the touch zone for each control key to its corresponding display area suffer from a problem in that they frequently experience "miss hits" wherein, through imprecision in the placement of the user's finger, the system selects a control key that differs from the one that the user desired to select.
In touch sensitive user interface systems that utilize the display area to define the touch zone for each control key, the frequency of "miss hits" can be reduced by enlarging the display area for each control key on the display panel. However, it is desirable to minimize the display area for each control key on the display panel because, as stated above, many systems that utilize touch sensitive user interfaces require that a large number of control keys be displayed on the display panel simultaneously. If the control key display area is enlarged, the number of control keys that can be simultaneously displayed is reduced.